The present invention relates generally to a device for holding individual screw blanks during the feeding of the blanks into and out of work stations which deform the blanks in some manner, for example, the cutting of flutes or the like in the extremity of the shank to form a drill point.
The invention more particularly relates to a collet which holds a screw blank which has previously been provided with radially extending wings and wherein the flutes to be formed in the shank must be oriented relative to the wings.
Self-drilling screws, for example, of the type typical of that shown in U.S. Pat. No. 3,125,923 generally include a plurality of flutes formed at the tip of a screw blank to form cutting edges and chip exhaust means. Such screws are typically manufactured utilizing high speed, multi-station apparatus such as that shown in U.S. Pat. No. 3,280,412 wherein screw blanks are fed individually into collet devices which are circumferentially spaced about a dial and which are received and retained in a pluality of pockets on the dial. The pockets permit the selective removal of the collets so that the apparatus may accommodate different sizes of blanks. The dial rotates about an axis, selectively carrying the screw blanks into a plurality of circumferentially spaced work stations where the various sawing operations are accomplished to form a drill tip configuation on the extremities of the blanks. A typical apparatus may include rotation inducing means which serve to rotate the blanks about their axes so that the various deformations of the blank created by the cutting operations may be accurately located and oriented relative to each other as the blank passes through the various work stations.
The accuracy and orientation of the various cutting operations are essential to the provision of an effective drill point. When the screw blank has been provided with one or more radially extending reaming wings which are to be located within the longitudinal dimensions of the flutes, the blanks must be oriented and fixed in a particular orientation lest the sawing operation will remove or harm the wings. Typical prior art devices do not consider the orientation of the first flute cut in the blank but rather performs the first operation randomly as the blank is fed into the collet. This obviously is inappropriate and unacceptable when the blank has been subjected to a previous forming operation, such as the formation of wings which must be oriented relative to the flutes.